update or replace [] on array field in mongodb - arrays

Question

So by mistake, I migrated 68k documents from a table to another, but the problem is ( i'm a SQL Server DBA learing mongodb):
I need a field ( array ) that has the value:
something : [ 000 ]
but during the project, I used another [ and ]:
$project:
{
field_name:[$field_value]
}
but the field is already array so the result I got was:
Vieweing with JASON:
"targetMarketCountryCode" : [
[
"076"
]
],
is there a way to update;replace this value to remove this quotes [[]] and use only one normal array quote []??
I would like to update ALL documents.
I'm trying to replace but with no success:
db.rep.replaceOne( {"field":[[079]]}), {"Idate":[079]} )
this is just a test, not the oficial table.
Tests:
db.teste.insert({name:"butter",value:[["077"]]})
db.teste.insert({name:"butter",value:[["077"]]})
db.teste.insert({name:"butter",value:[["077"]]})
db.teste.find()
/* 1 createdAt:14/08/2019 13:08:15*/
{
"_id" : ObjectId("5d5431ef44f85649486e4100"),
"name" : "butter",
"value" : [
[
"077"
]
]
},
/* 2 createdAt:14/08/2019 13:08:21*/
{
"_id" : ObjectId("5d5431f544f85649486e4101"),
"name" : "butter",
"value" : [
[
"077"
]
]
},
/* 3 createdAt:14/08/2019 13:08:22*/
{
"_id" : ObjectId("5d5431f644f85649486e4102"),
"name" : "butter",
"value" : [
[
"077"
]
]
}
///////////////////////////////////////////////////////
db.teste.aggregate({$unwind: "$value"})
/* 1 createdAt:14/08/2019 13:08:15*/
{
"_id" : ObjectId("5d5431ef44f85649486e4100"),
"name" : "butter",
"value" : [
"077"
]
},
/* 2 createdAt:14/08/2019 13:08:21*/
{
"_id" : ObjectId("5d5431f544f85649486e4101"),
"name" : "butter",
"value" : [
"077"
]
},
/* 3 createdAt:14/08/2019 13:08:22*/
{
"_id" : ObjectId("5d5431f644f85649486e4102"),
"name" : "butter",
"value" : [
"077"
]
}
////////////////////////////////////////////////////
db.teste.aggregate([{$unwind:"$value"}, {$out:"teste" }])
db.teste.find()
/* 1 createdAt:14/08/2019 13:08:15*/
{
"_id" : ObjectId("5d5431ef44f85649486e4100"),
"name" : "butter",
"value" : "077"
},
/* 2 createdAt:14/08/2019 13:08:21*/
{
"_id" : ObjectId("5d5431f544f85649486e4101"),
"name" : "butter",
"value" : "077"
},
/* 3 createdAt:14/08/2019 13:08:22*/
{
"_id" : ObjectId("5d5431f644f85649486e4102"),
"name" : "butter",
"value" : "077"
}
What I can see is:
1) I have an array with [["value"]]
2) Using $unwind I can replace [["value"]] to ["value"].
3) Uing it to "update" the document, it removes both arrays and replace the value with a simple string.

Answer 1

For the MongoDB version: 4.2+
db.rep.updateMany(
{},
[
{
$set: {
"targetMarketCountryCode": {
$arrayElemAt: ["$targetMarketCountryCode",0]
}
}
}
]
)
It would replace the 'targetMarketCountryCode' array with its first element in all the documents.
For lower versions: 2.6+
db.rep.aggregate([
{
$unwind:"$targetMarketCountryCode"
},
{
$out:"rep"
}
])
It performs aggregation on the 'rep' collection. The 'targetMarketCountryCode' is unwinded and old data of the collection is replaced with the output of the aggregation query.
Sample data:
{
"_id" : ObjectId("5d5430aa7c780d119a01a6ce"),
"targetMarketCountryCode" : [
[
"076"
]
]
}
Output:
{
"_id" : ObjectId("5d5430aa7c780d119a01a6ce"),
"targetMarketCountryCode" : [
"076"
]
}

Answer 2

Thank you guys for the answers. As i'm using mongo 4.0 I could make this:
db.collection.update({ field: [["value"]] }, {
$set: {
"field": [ "value" ]},
{ multi: true, upsert: false}})